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Types of Ball Valve

Duplex ball valve

There are five general body styles of ball valves: single body, three-piece body, split body, top entry, and welded. The difference is based on how the pieces of the valve—especially the casing that contains the ball itself are manufactured and assembled. The valve operation is the same in each case.

In addition, there are different styles related to the bore of the ball mechanism itself.

Ball valves in sizes up to 2 inch generally come in single piece, two or three piece designs. One piece ball valves are almost always reduced bore, are relatively inexpensive and generally are throw-away. Two piece ball valves are generally slightly reduced (or standard) bore, they can be either throw-away or repairable. The 3 piece design allows for the center part of the valve containing the ball, stem & seats to be easily removed from the pipeline. This facilitates efficient cleaning of deposited sediments, replacement of seats and gland packings, polishing out of small scratches on the ball, all this without removing the pipes from the valve body. The design concept of a three piece valve is for it to be repairable.

Full port

A full port or more commonly known full bore ball valve has an over-sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted but the valve is larger and more expensive so this is only used where free flow is required, for example in pipelines which require pigging.

Reduced port

In Reduced port (more commonly known as reduced bore) ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in flow area being smaller than pipe. As the flow discharge remains constant and is equal to area of flow times velocity, the velocity increases with reduced area of flow.

V port

A V port ball valve has either a 'v' shaped ball or a 'v' shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced the small end of the 'v' is opened first allowing stable flow control during this stage. This type of design requires a generally more robust construction due to higher velocities of the fluids, which might damage a standard valve. These can be referred to as a type of control valve but are not as accurate as a balancing valve, needle valve, globe valve, or pressure regulating valve.

Cavity filler

Many industries encounter problem with residues in the ball valve. Where the fluid is meant for human consumption, residues may also be health hazard, and when where the fluid changes from time to time contamination of one fluid with another may occur. Residues arise because in the half open position of the ball valve a gap is created between the ball bore and the body in which fluid can be trapped. To avoid the fluid getting into this cavity, the cavity has to be plugged, which can be done by extending the seats in such a manner that it is always in contact with the ball. This type of ball valve is known as Cavity Filler Ball Valve.

There are a few types of ball valves lateral movement of the ball:

Trunnion

A trunnion ball valve has additional mechanical anchoring of the ball at the top and the bottom, suitable for larger and higher pressure valves (say, above 10 cm and 40 bars).

A floating ball valve is one where the ball is not held in place by a trunnion. In normal operation, this will cause the ball to float downstream slightly. This causes the seating mechanism to compress under the ball pressing against it. Furthermore, in some types, in the event of some force causing the seat mechanism to dissipate (such as extreme heat from fire outside the valve), the ball will float all the way to metal body which is designed to seal against the ball providing a somewhat failsafe design.

Manually operated ball valves can be closed quickly and thus there is a danger of water hammer. Some ball valves are equipped with an actuator that may be pneumatically, hydraulically or motor operated. These valves can be used either for on/off or flow control. A pneumatic flow control valve is also equipped with a positioner which transforms the control signal into actuator position and valve opening accordingly.

Multiport

Three- and four-way have an L- or T-shaped hole through the middle. The different combinations of flow are shown in the figure. It is easy to see that a T valve can connect any pair of ports, or all three, together, but the 45 degree position which might disconnect all three leaves no margin for error. The L valve can connect the center port to either side port, or disconnect all three, but it cannot connect the side ports together.

Multi-port ball valves with 4 ways, or more, are also commercially available, the inlet way often being orthogonal to the plane of the outlets. For special applications, such as driving air-powered motors from forward to reverse, the operation is performed by rotating a single lever four-way valve. The 4-way ball valve has two L-shaped ports in the ball that do not interconnect, sometimes referred to as an "×" port.

A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball (called a "floating ball") to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's status.

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications, where they are often preferred to gates and globe valves, but they lack their fine control in throttling applications.

The ball valve's ease ofoperation, repair, and versatility lend it to extensive industrial use, supporting pressures up to 1000 bar andtemperatures up to 752°F (500°C), depending on design and materials used. Sizes typically range from 0.2 to 48 inches (0.5 cm to 121 cm). Valve bodies are made of metal, plastic, or metal with a ceramic; floating balls are often chrome plated for durability.

Ball valves can be used in a variety of applications and markets, such as transmission and storage, gas processing, industrial, and many more. Ball Valves provide reliable leak protection which is especially beneficial in gas applications. Ball valves have low pressure drop and can open and close quickly.

Chemical and Petrochemical Complexex

Low Differential Pressure Control

Emission Control

Handle Highly Viscous Fluids. Abrasive Slurries or Corrosive as well as non-corrosives in processes and Storing Facilities

Power Industry

Boiler Feed Water Control

Control abd Shot-off for Steam

Burner Trip Valves

Sluicing Valves for Feding Coal into Pressurised Combustore and for extracting fly ash

Gas and Oil Production

Subsea Isolation and Shut-down

Well-Head Isolation

Piping Suege Control

Secondary and Enhanced Oil Recovery

Processing Separration

Transmission and Distribution

Storage Tang

Pulp and paper Industry

Pulp Mill Diagesters

Shut-off Valves

Batch-Digester Blow Service

Liquor Fill and Circulation

Lime Mud (Slrry) Flow Contro

Dilution Water Control

Other Common area for the application of ball valves include: Food Industry. Water supply and transport, Marine and soilds transport.

Micro-resistance Ball Valve uses the rubber covered roller as the disc, which, under the action of the medium, can roll up and down along with the sliding path inside the valve so as to open or close it. And it features by the big flow, small flow-resistance loss, good tightness, silent close and reduced water shock wave. It can be mountable vertically or horizontally and used on the outlet of the water pump of the cold-water, hot-water, industrial and living sludge pipe networks to prevent the medium from going back.

Spring Loaded Pressure Relief Valve

The basic spring loaded pressure Relief Valve has been developed to meet the need for a simple, reliable, system actuated device to provide overpressure protection. The image on the right shows the construction of a spring loaded pressure Relief Valve. The Valve consists of a Valve inlet or nozzle mounted on the pressurized system, a disc held against the nozzle to prevent flow under normal system operating conditions, a spring to hold the disc closed, and a body/Bonnet to contain the operating elements. The spring load is adjustable to vary the pressure at which the Valve will open.

When a pressure Relief Valve begins to lift, the spring force increases. Thus system pressure must increase if lift is to continue. For this reason pressure Relief Valves are allowed an overpressure allowance to reach full lift. This allowable overpressure is generally 10% for Valves on unfired systems. This margin is relatively small and some means must be provided to assist in the lift effort. Most pressure Relief Valves, therefore, have a secondary control chamber or huddling chamber to enhance lift. As the disc begins to lift, fluid enters the control chamber exposing a larger area of the disc to system pressure.

This causes an incremental change in force which overcompensates for the increase in spring force and causes the Valve to open at a rapid rate. At the same time, the direction of the fluid flow is reversed and the momentum effect resulting from the change in flow direction further enhances lift. These effects combine to allow the Valve to achieve maximum lift and maximum flow within the allowable overpressure limits. Because of the larger disc area exposed to system pressure after the Valve achieves lift, the Valve will not close until system pressure has been reduced to some level below the set pressure. The design of the control chamber determines where the closing point will occur. The difference between the set pressure and the closing point pressure is called blowdown and is usually expressed as a percentage of set pressure.

Balanced Bellows Valves and Balanced Piston Valves

When superimposed back pressure is variable, a balanced bellows or balanced piston design is recommended. A typical balanced bellow is shown on the right. The bellows or piston is designed with an effective pressure area equal to the seat area of the disc. The Bonnet is vented to ensure that the pressure area of the bellows or piston will always be exposed to atmospheric pressure and to provide a telltale sign should the bellows or piston begin to leak. Variations in back pressure, therefore, will have no effect on set pressure. Back pressure may, however, affect flow.

Other Designs of Pressure Relief Valves

Safety Valve.

A safety Valve is a pressure Relief Valve actuated by inlet static pressure and characterized by rapid opening or pop action. (It is normally used for steam and air services.)

Low-Lift Safety Valve

A low-lift safety Valve is a safety Valve in which the disc lifts automatically such that the actual discharge area is determined by the position of the disc.

Full-Lift Safety Valve

A full-lift safety Valve is a safety Valve in which the disc lifts automatically such that the actual discharge area is not determined by the position of the disc.

Relief Valve

A Relief Valve is a pressure relief device actuated by inlet static pressure having a gradual lift generally proportional to the increase in pressure over opening pressure. It may be provided with an enclosed spring housing suitable for closed discharge system application and is primarily used for liquid service.

Safety Relief Valve

A safety Relief Valve is a pressure Relief Valve characterized by rapid opening or pop action, or by opening in proportion to the increase in pressure over the opening pressure, depending on the application and may be used either for liquid or compressible fluid.

Conventional Safety Relief Valve

A conventional safety Relief Valve is a pressure Relief Valve which has its spring housing vented to the discharge side of the Valve. The operational characteristics (opening pressure, closing pressure, and relieving capacity) are directly affected by changes of the back pressure on the Valve.

Balanced Safety Relief Valve

A balanced safety Relief Valve is a pressure Relief Valve which incorporates means of minimizing the effect of back pressure on the operational characteristics (opening pressure, closing pressure, and relieving capacity).

Pilot-Operated Pressure Relief Valve

A pilotoperated pressure Relief Valve is a pressure Relief Valve in which the major relieving device is combined with and is controlled by a self-actuated auxiliary pressure Relief Valve.

Power-Actuated Pressure Relief Valve

A poweractuated pressure Relief Valve is a pressure Relief Valve in which the major relieving device is combined with and controlled by a device requiring an external source of energy.

Temperature-Actuated Pressure Relief Valve

A temperature-actuated pressure Relief Valve is a pressure Relief Valve which may be actuated by external or internal temperature or by pressure on the inlet side.

Vacuum Relief Valve

A vacuum Relief Valve is a pressure relief device designed to admit fluid to prevent an excessive internal vacuum; it is designed to reclose and prevent further flow of fluid after normal conditions have been restored.

A pressure Relief Valve is a safety device designed to protect a pressurized vessel or system during an over pressure event. An overpressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP). The primary purpose of a pressure Relief Valve is protection of life and property by venting fluid from an overpressurized vessel.Many electronic, pneumatic and hydraulic systems exist today to control fluid system variables, such as pressure, temperature and flow. Each of these systems requires a power source of some type, such as electricity or compressed air in order to operate. A pressure Relief Valve must be capable of operating at all times, especially during a period of power failure when system controls are nonfunctional. The sole source of power for the pressure Relief Valve, therefore, is the process fluid. Once a condition occurs that causes the pressure in a system or vessel to increase to a dangerous level, the pressure Relief Valve may be the only device remaining to prevent a catastrophic failure. Since reliability is directly related to the complexity of the device, it is important that the design of the pressure Relief Valve be as simple as possible.

The pressure Relief Valve must open at a predetermined set pressure, flow a rated capacity at a specified overpressure, and close when the system pressure has returned to a safe level. Pressure Relief Valves must be designed with materials compatible with many process fluids from simple air and water to the most corrosive media. They must also be designed to operate in a consistently smooth and stable manner on a variety of fluids and fluid phases.

Safety valves (sometimes called relief valves or safety relief valves) are spring loaded devices. Normally, the valve is forced shut by the spring, but when the pressure rises, the force of the spring is overcome, forcing the valve open. This releases fluid, relieving the pressure. Once the process pressure is reduced, the safety valve will re seal, limiting the amount of material released.

Pressure and / or vacuum relief valves are used on liquid storage tanks and other process vessels or systems to prevent structural damage due to excess internal pressure or vacuum. Storage tanks are pressurized when liquid is pumped in, compressing the existing vapor or when rising temperatures cause increased evaporation or expansion of existing vapor. Conversely, a vacuum condition may be created when pumping out or due to falling temperature. To prevent tank damage, vapor must be allowed into or out of the tank at specified pressure / vacuum conditions. The volume rate of venting depends upon the tank size, volatility of the tank contents, the pumping rates and the temperature.

We pressure relief valves help meet the requirements of ANSI/ASHRAE 15-2001 Safety Standard for Refrigeration Systems as well as other worldwide codes. This standard requires pressure vessels of all refrigeration systems to be protected by a pressure relief device or other approved means to safely relieve pressure in the event of fire or other abnormal conditions. Once installed, a properly selected we pressure relief valve is ready to vent to atmosphere any temporary excessive overpressure inside of a vessel. After discharge, these valves will attempt to reseat to minimize loss of refrigerant. However, once any relief valve has discharged, it must be replaced as soon as possible because debris may have settled on the seat during discharge.

We pressure relief valves should be connected to the....

vapor space of refrigerant vessels,

Heat Exchangers,

Oil Pots,

Oil Stills,

Pilot Receivers,

and elsewhere as may be required by various codes. Where dual pressure relief valves are required, we offers the three-way valves and other components necessary for assembly. Rupture disc assemblies are required when using we pressure relief valves for halocarbon applications because the high cost of such refrigerants demands extreme tightness, These pressure relief valves offer a cartridge style design for ease of replacement without disturbing the piping. EZ-SRV pressure relief valves are available in pressure ratings to 600 psi.

Tank protection equipment typically includes an operating valve which is designed to provide pressure/vacuum relief under normal pump in/out and thermal breathing conditions. An emergency relief valve can also provide both pressure and vacuum relief and normally it is sized to provide pressure relief if there is a fire in the immediate vicinity of the tank. It may also be sized by the tank designer to provide protection in the event of equipment failure (such as the rupture of a process steam line or an inert gas ba nketing system failing “wide open”) or operator error.

A typical tank installation is shown n Figure 1 which includes the following Groth products:

Pressure/Vacuum Weight Loaded Valve

Gas Blanketing Regulator

Emergency Pressure Relief Valve

Pressure Relief

As the pressure in the storage tank increases, the vacuum pallet is held shut. When the set pressure is reached, the pressure pallet lifts and relieves tank pressure to the atmosphere (or to a header if it is a pipe away valve). See Figure 2.

Vacum Relief

As a vacuum is drawn in the storage tank (for example, when fluid is being pumped out), the pressure pallet is held shut. When the vacuum setting is reached, the vacuum pallet lifts and air is drawn into the tank from the atmosphere. See Figure 3.

Body Designs of Globe Valves

There are three primary body designs for Globe valves, namely:

Tee Pattern or Z-body

Angle Pattern

Wye Pattern or Y-body body

Tee Pattern or Z-shaped Globe Valve Design

Tee Pattern Globe valve design is the most common body type, with a Z-shaped diaphragm. The horizontal setting of the seat allows the stem and disk to travel perpendicular to the horizontal line. This design has the lowest coefficient of flow and higher pressure drop. They are used in severe throttling services, such as in bypass lines around a control valve. Tee-pattern Globe valves may also be used in applications where pressure drop is not a concern and throttling is required.

Angle Body Globe Valve

Angle Pattern Globe valves design is a modification of the basic Tee Pattern Globe valve. The ends of this Globe valve are at an angle of 90 degrees, and fluid flow occurs with a single 90 degrees turn. They have a slightly lower coefficient of flow than wye-pattern Globe valves. They are used in applications that have periods of pulsating flow because of their capability to handle the slugging effect of this type of flow.

Wye Pattern Globe valves

Wye Pattern Globe valves design, is an alternative for the high pressure drop, inherent in Globe valves. Seat and stem are angled at approximately 45 degrees, what gives a straighter flowpath at full opening and offer the least resistance to flow. They can be cracked open for long periods without severe erosion. They are extensively used for throttling during seasonal or startup operations. They can be rod through to remove debris when used in drain lines that are normally closed.

Introduction of Globe Valves

As their name suggests, globe valves are linear motion valves with rounded globular shaped bodies. Since their shape is similar to other valve bodies, positive identification must be made based on internal piping. Recently globe valves have lost their traditional round body-shape. Globe valves have many advantages and disadvantages for users. They have excellent and precise throttling ability for high-pressure systems. The disadvantages include low-flow coefficients and a longer operating time because the operator must turn the handle and stem many times to ensure the valve is completely open or completely closed. Globe valves can be used in systems that require frequent stroking, vacuum, and systems that have a wide range of temperature extremes

A Globe valves is a linear motion valve and are primarily designed to stop, start and regulate flow. The disk of a Globe valve can be totally removed from the flowpath or it can completely close the flowpath.

Conventional Globe valves may be used for isolation and throttling services. Although these valves exhibit slightly higher pressure drops than straight=through valves (e.g., gate, plug, ball, etc.), they may be used where the pressure drop through the valve is not a controlling factor.

Because the entire system pressure exerted on the disc is transferred to the valve stem, the practical size limit for these valves is NPS 12 (DN 300). Globe valves larger than NPS 12 (DN 300) are an exception rather than the rule. Larger valves would require that enormous forces be exerted on the stem to open or close the valve under pressure. Globe valves in sizes up to NPS 48 (DN 1200) have been manufactured and used.

Globe valves are extensively employed to control flow. The range of flow control, pressure drop, and duty must be considered in the design of the valve to avert premature failure and to assure satisfactory service. Valves subjected to high-differential pressure-throttling service require specially designed valve trim.

Generally the maximum differential pressure across the valve disc should not exceed 20 percent of the maximum upstream pressure or 200 psi (1380 kPa), whichever is less. Valves with special trim may be designed for applications exceeding these differential pressure limits.

Typical Applications of Globe valves

The following are some of the typical applications of Globe valves:

Cooling water systems where flow needs to be regulated

Fuel oil system where flow is regulated and leaktightness is of importance

High-point vents and low-point drains when leaktightness and safety are major considerations

Boiler vents and drains, main steam vents and drains, and heater drains

Turbine seals and drains

Turbine lube oil system and others

A globe valve, different from ball valve, is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.

Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc ordisk. In globe valves, the plug is connected to a stem which is operated by screw action using a handwheel in manual valves. Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly.